Since the 1970s, scholars have invoked parental investment theory to explain why men appear to be more interested in sexual pursuits than women (Trivers, Reference Trivers and Campbell1972). The explanation has been: Men have less to lose from a poor mating choice, and so they make mating decisions more capriciously, they seek out sexual opportunities with greater fervor, and they have lower standards. The influence of the parental investment perspective and its descendants is hard to overstate.

In this light, the theoretical implications of the contribution offered by Wahring et al. are potentially massive. Their explanation for gender differences flips the parental-investment logic on its head: What if these differences flow not from the fact that men have less to lose from sexual pursuits than women do, but rather that they have more to gain? Perhaps single men are operating from a support deficit because they are lonelier than single women, they have fewer intimate partners in other corners of their lives, and they suffer more in the absence of a partner. Therefore, men may be more likely to experience attraction in first encounters, to initiate sex, and to profess their love not because they are incautious but because they are desperate.

This new support-deficit perspective shifts the scientific playing field as dramatically as any single paper can. Yes, men initiate sex with greater ardor than women do. But men are also more likely than women to believe that they need a romantic partner to be happy, to resist breakups/divorces, and to remain emotionally attached to their exes. In other words, Wahring et al. deftly illustrate how the gender difference extends beyond sex; it spans relationship initiation, maintenance, breakup, and the aftermath. And whereas a support-deficit perspective accounts for all these gendered phenomena, parental investment perspectives can credibly accommodate only a fraction of them.

One classic argument could perhaps maintain an essential role for the parental investment perspective: If short-term, casual sex were governed by one type of mating system, but long-term relationships were governed by another, then parental investment perspectives might explain the former and social-deficit perspectives might explain the latter. Indeed, some perspectives suggest that casual sex and long-term commitments derive from independent mental systems (Buss & Schmitt, Reference Buss and Schmitt1993; Li & Meltzer, Reference Li and Meltzer2015). According to this view, Wahring et al.’s link between men’s greater pursuit of sex and their greater reluctance to end committed relationships is akin to mixing apples and oranges.

Nevertheless, this attempt to bolster the parental-investment perspective fails to contend with the fact that the short-term vs. long-term distinction is not what it used to be. Of course, people imagine different things when they think about short-term, casual trysts or long-term committed relationships. The problem is that the independent-mechanisms argument mischaracterizes how humans initiate relationships in real life. In most cases, relationships are not obviously “about” short-term sex or long-term bonding until they are well underway (Eastwick et al., Reference Eastwick, Keneski, Morgan, MacDonald and Huang2018). That is, people commonly have no idea whether they want a relationship with a given partner to be short-term or long-term until they have had a sexual experience with them. On average, the uninspiring sexual experiences are more likely to become short-term relationships – bland hookups fizzle – whereas the inspiring ones beget full-fledged, long-term relationships (Eastwick, Finkel, & Simpson, Reference Eastwick, Finkel and Simpson2019).

The primary reason humans mate this way is that we are creatures with remating preferences (Prum, Reference Prum2018). We seek compatibility, but assessing it takes time, and so we have to test the waters repeatedly with prospective mates until things start (or fail) to click (Eastwick, Finkel, & Joel, Reference Eastwick, Finkel and Joel2023). Sex is a key component of this testing and retesting process; after all, cultivating “love and commitment” is one of the most popular reasons that both men and women have sex (Meston & Buss, Reference Meston and Buss2007). Taken together, the support-deficit framework predicts that men would be a little more eager than women to have sex, yes, but also more eager to have a second date, to fall in love, and to stroll hand-in-hand through Ikea.

Is my “a little more eager” characterization fair when it comes to gender differences in the sex drive? Mostly, yes. When people are describing how they feel about a real-life partner that they actually know, gender differences in sexual desire are meta-analytically small in initial attraction settings (d = .28; Fletcher et al., Reference Fletcher, Kerr, Li and Valentine2014) and ongoing relationships (d = .27 Frankenbach et al., Reference Frankenbach, Weber, Loschelder, Kilger and Friese2022). These effect sizes fit squarely within the range of the gender differences that Wahring et al. have documented, so they plausibly share the same support-deficit source.

Gender differences are larger under some circumstances, like when people are approached for casual sex by a stranger (d = 1.11; Hald & Høgh-Olesen, Reference Hald and Høgh-Olesen2010), or when people say “yes” to dates on Tinder (d = 1.25; Gerrard, Reference Gerrard2021). Perhaps parental investment perspectives can best explain these larger differences. The trouble, however, is that propositioning strangers and swiping on apps are uniquely contemporary experiences. The evaluation of romantic partners in ancestral contexts would primarily have taken place in small groups and extended networks of known others (Eastwick, Reference Eastwick2026). The relevance of evolved parental-investment mechanisms to these very large gender differences is, therefore, questionable. Other explanations – like women’s pessimistic views of male strangers’ sexual skills and propensity for violence (Conley & Klein, Reference Conley and Klein2022) – will likely be needed to explain why gender differences become so large in the anonymous contexts that were rare in hunter-gatherer settings.

Wahring et al. do not push their thesis as far as I have. But in my view, it is both warranted and transformative. Surely, there exist some mating-domain gender differences where parental investment perspectives will prove necessary. But given that social deficits appear to play a role across the full time-scale of human relationships – from before they begin until well after they end – a parental-investment perspective should be invoked when the gender difference is both (a) larger than what can be explained by social deficits alone, and (b) unambiguously relevant to ancestral contexts. Otherwise, social deficits offer the parsimonious explanation.